Also known as a reverse lipogram. Whereas lipograms are a form of constrained writing where a particular letter is completely omitted from the text, an antilipo is entirely comprised of words containing a particular letter, as illustrated by this example -
The predator alongside the feline sailed
Inside one pea green barge
They carried honey, their plentiful money
Enclosing their bounteous charge
The feathered one spied the heavenly views
Then mouthed one tune, fingering frets
"Dear Feline, the beautiful kitten we choose
Seeing thee, we bear zero regrets"...
The remainder of this poem, along with a lipogrammatic Owl and the Pussycat, can be found at http://uk.geocities.com/willhelston/lipogram.html . The author, Will Thomas, is also the inventor of the term "antilipo".